1. Field
The embodiments discussed herein are directed to a digital signature system and a digital signing method capable of assuring the validity of partially extracted streaming data and allowing a third party to certify the streaming data.
2. Description of the Related Art
Installation of surveillance cameras and installation of drive recorders in business vehicles have become widespread in recent years.
Accordingly, motion pictures captured by such apparatuses are often presented as evidences.
Conversations between clients and operators are recorded and the recorded conversations are held as evidences in order to take measures against troubles in telephone transactions or support businesses.
In use of motion pictures or sounds as evidences, media on which the motion pictures or sounds are recorded are directly presented nowadays. The media include video tapes, image files, audio files.
In addition, apparatuses and recording media are digitized in recent years. It is generally easy to tamper or edit digitized information, compared with analog information. Accordingly, when the digital information is presented as evidences, it is necessary to perform verification by third parties, such as digital signature or time stamping.
In the direct presentation of the media on which motion pictures or sounds are recorded, part of the data on the media, which is not related to the evidences, is also presented.
Use of personal private information is often restricted in recent years, and it is required to indicate or partially delete such information in response to their own requests.
In order to fulfill the requirement, studies of signature technologies are advancing in which the originality (integrity) of part of electronic documents is assured or partially concealed (filled with black).
For example, conventionally a partial integrity assurance technology (PIAT) is disclosed in order to resolve a problem in which partial concealment of a document makes it impossible to verify a signature attached to the document). Application of the PIAT allows signatures attached to electronic documents to be verified even in a state where the electronic documents are partially filled with black and also allows third parties to certify that the documents are not altered excluding the parts filled with black (modification or addition is allowed in the parts).
However, when part of large data, such as motion pictures or sounds for long times, is extracted, the amount of information related to the signature is greatly increased with the conventional technology described above.